Amyotrophic lateral sclerosis (ALS), more commonly known as Lou Gehrig’s disease, is a neurodegenerative disease that causes eventual respiratory failure due to motor neuron death. Approximately 90% of all ALS cases are classified as sporadic ALS, meaning that there is no known cause. The remaining 10% of cases are classified as familial ALS, and of these, 2% have been linked to the gene for SOD1. This gene encodes the copper-zinc superoxide dismutase protein, an antioxidant enzyme which catalyzes the reduction of the superoxide radical (O2-) to hydrogen peroxide, which can then be further broken down into water and diatomic oxygen via hydrogen peroxidases. In vivo, metals bound to the wild-type protein are the catalyst for the reduction of superoxide, but certain mutants exhibit different metal-binding properties. We prepared and purified numerous protein variants using column chromatography methods, as well as their apoprotein variants through the standard dialysis method of metal removal. The prepared apoproteins were then titrated with metals such as copper, zinc and cobalt to prepare various derivatives of the mutants. These mutants were monitored by UV-Visible spectrophotometry in order to determine metal-binding. The results suggest, contrary to previous results, that these apoprotein variants of mutants such as L38V and G93A can be correctly metallated under the proper conditions. The implications are that proper metallation may be a matter of a kinetic versus a thermodynamic product, which future research will hopefully elucidate with respect to the functioning of the metal-binding sites of this protein, along with its implications for ALS.
Sean Lehman, ’10 Spencer, IA
Majors: Biochemistry and Molecular Biology, Integrated Psychosocial Theory
Sponsor: Cynthia Strong